There are many applications where an array of measurement sensors is deployed to collect dynamic physical event data, such as seismic shock, vibration, temperature, strain or humidity in industrial manufacturing and testing processes, remote machinery condition monitoring, building structure monitoring, etc. A problem that arises in data collection from such events is that the data, typically dynamic analog data at various frequencies, is collected using expensive instrumentation devices. These instruments are connected to each other via various networks with phase delays, even though taken simultaneously due to differences in network path lengths or slight local clock differences or circuit latency. The kind of measurement system that cannot measure the dynamic data with synchronized clock will make the data acquisition meaningless. For example, if two channels of data are all acquired at 12:00 pm while one of them is marked as 12:01 pm, the time delay or error of the time clock will cause these two signals to be out of phase so that they cannot be compared and used together. Therefore for dynamic data measurement using multiple sensors, acquiring the data at the “same time”, meaning, with time synchronization technology, is critical.
U.S. Pat. No. 6,469,639 discloses a method of collecting data from a plurality of sensors, including shock and vibration sensors. The method includes converting the plurality of sensor analog signals into digital data, processing the digital data, generating a data communications protocol for communicating the digital data, and simultaneously and remotely detecting the generated communications data. A data communications processor controls power management of the data acquisition processing circuit.
U.S. Pat. No. 7,200,158 discloses a method of synchronizing data across a network with a device that recognizes the time synchronization packet and substitutes a real-time value from the master internal counter into the proper place in a data packet that is placed between an Ethernet Media Access Controller (MAC) and a Physical Interface Transceiver (PHY). A second device monitors the packet passing from the MAC to the PHY and determines when it is a time synchronization packet from the time master. Upon recognition of the proper packet, the second device simultaneously captures the master's time value and captures the value of a local real-time clock. The result of these captures are presented to the local host computer which controls the time base clock that increments the local real-time clock to either speed up or slow down this local clock, thereby synchronizing the local clock to the time master clock. The offset and skew of the local clock to the master clock is reduced to only the network latency plus variability due to network congestion.
European patent application 2288215 discloses a method for exchanging data between a plurality of sensors and/or actuators and an appropriate destination in a core network.
U.S. Published Application 2013/0246543 discloses networked sensor devices configured to obtain sensor readings from one or more sensors and then store the sensor readings in a server by way of a wireless or wired network using Ethernet protocol for communication of sensor information.
U.S. Published Application 20140088873 discloses use of Ethernet protocol for devices that integrate sensors for dissemination of lightning data over wired or wireless networks. The apparatus features a communication jack that houses a communication port, a sensor and a sensor data server. The server is coupled with both the port and the sensor and is configured to obtain sensor data from the sensor and provide access to the sensor data via the communication port. The system is a plurality of such communication jacks distributed over a geographic range.
Power over Ethernet (PoE), described at http://en.wikipedia.org/wiki/Power_over_Ethernet, is a power supply technology for Ethernet wiring where, in one mode called “Mode B”, spare lines of Cat 5 or Cat 6 cable are energized by line drivers capable of sourcing a few milliamperes of current that is sufficient to obtain all required electrical power for a remote device through the lines. In another mode called “Mode A”, power can be carried on the data lines. In either situation, a host can provide power to remote devices such as switches, IP phones and the like.
An object of the invention was to reduce packaging size for remote sensors of a sensor array, while increasing the flexibility of supporting large voltage drops in long cables, and reducing the cost.
Another object of the invention was to devise an array of high speed remote sensors that measure analog physical signals and can gather data from a single event or vibration source at a central server for recording or display, with synchronization to account for phase delays and the like among individual remote sensors.